The present invention relates to an integrated circuit device having a memory area comprising a data memory.
Such integrated circuit devices are widely used in applications where information processing security is essential. In particular, these are integrated circuit cards including applications relating to the fields of health, mobile telephony, or also banking applications.
An integrated circuit card is composed of a plastic card body which incorporates an electronic unit. This card communicates with a terminal, for example a mobile telephone, a banking terminal or also a computer, through a communications network and is able to send messages containing encrypted information to said terminal through the network so as to make information transfers secure. In everyday language, the message is said to be signed. For computing encrypted information, the card employs a secret coding key which is located within the data memory of its memory area and an encryption algorithm.
Although information transfers are thus made secure, an integrated circuit card remains vulnerable since a forger could perform many actions on the card which would allow him or her to uncover its secrets. Thus, said forger, wishing to find the coding key, could for example send a signature instruction message to the card and keep a record of the signals generated when executing said instruction. Thereafter, he or she could send a large number of signature instructions for the same message, expose the card to electromagnetic perturbations at specific time points during the progress of said algorithm and keep records of the various emitted signals. By matching records of signals obtained during perturbations with the first record, forgers can analyze differences or the absence of differences between the various obtained encrypted pieces of information in order to uncover a cod key portion. Thus, in spite of the secure information transfer performed by the card, forgers can still access confidential information by performing a very large number of actions on the integrated circuit card.
Thus, a technical problem to be solved by the present invention is to provide an integrated circuit device having a memory area comprising a data memory, which device would allow the card to become more secure by restricting the number of forgery actions that can be performed on the card.
According to the present invention, a solution to the technical problem posed is such that the data memory contains at least one counter element, and at least one threshold value, which counter element, on the one hand, counts at least one number of event occurrences within said device, and, on the other hand, is likely to reach said threshold value which is indicative of a large maximum number of occurrences of said events, wherein the data memory comprises at least two indicator elements residing at non-contiguous locations within the data memory, said indicator elements being associated with said counter clement and said indicator element being designed to go from a first state to a second state when said counter element has reached said threshold value.
Thus, as explained in detail below, the device according to the invention enables to restrict the number of possible actions or events performed on said integrated circuit card, on the one hand, by means of a counter element which will count the number of actions performed taking into account an action or a group of actions, and, on the other hand, by means of an indicator element which will indicate that the threshold value of the event or action occurrence number has been reached, so that afterwards, a sanction can be applied the next time said threshold value is exceeded.
Other features and advantages of the invention will become apparent in the following description of preferred embodiments of the present invention, provided by way of non-limiting examples, in reference to the appended figures.